Integration of CVD Prevention Into Cancer Survivorship

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Introduction

The American Cancer Society predicts that by 2024, there will be 19 million long-term survivors of cancer in the United States.1 Cardiovascular disease (CVD) is the leading cause of death in many survivors of cancer, and cardiovascular risk factors are more prevalent compared with age-matched controls.2,3 Survivors of cancer are therefore a rapidly growing, high-risk population with increasing but still relatively under-focused preventative efforts. Because CVD in survivors of cancer shares the same underlying pathophysiological mechanisms as the general population, the same interventions apply. Recognition of increased risk and modification of traditional risk factors remains the most effective strategy for primary prevention in this population.

An Important Transition to Survivorship

Clinicians caring for patients with cancer are familiar with the concept of competing risks whereby therapies aimed at combating cancer are weighed against the potential for adverse outcomes from other diseases. As patients with cancer enter long-term survivorship (generally defined as >5 years from diagnosis), the risk of death from CVD rivals, and in many cases exceeds, that of recurrent or de novo cancer. This period is an important time for CVD prevention whereby primary care efforts move to the foreground, with many patients transitioning back to traditional primary care settings and some patients continuing with their oncologist. This transition represents a logistically difficult but critically important moment in the care of a survivor of cancer. In 2006, the Institute of Medicine identified the need for a survivorship plan, noting that many patients are lost in this transition.4 Subsequently, survivorship guidelines for those with breast or prostate cancer have been published with prevention of CVD as a prominent focus.5-7

One potential downside to cancer-specific survivorship guidelines as they pertain to CVD prevention is that primary care clinicians may become entangled in the complexities of each cancer's specific treatment effects on CVD (androgen deprivation therapy, for instance) and lose sight of the big picture. Despite the ever-growing armamentarium and complexity of novel cancer therapeutics and well-publicized cardiotoxicities of some of those therapies, the majority of CVD risk for the average survivor of cancer is driven by traditional cardiovascular risk factors. The greatest reduction in risk is likely to be achieved by following primary prevention guidelines created for the general adult population (Table 1).8-14

Table 1

Estimating Risk

The pooled cohort risk equation (http://tools.acc.org/ASCVD-Risk-Estimator/) created for the American College Cardiology (ACC) and American Heart Association (AHA) 2013 Guidelines on the Assessment of Cardiovascular Risk is the most widely used initial tool for risk discussions.15 Elevated risk estimates support treatment decisions, such as the initiation of lipid-lowering therapy but also, perhaps more importantly, frame the provider-patient discussion and prioritize lifestyle changes. Most survivors of cancer would be expected to fall into the intermediate risk (5 to <7.5% 10-year risk of atherosclerotic CVD [ASCVD]) or high risk (≥7.5%) estimates due to age and shared cardiovascular risk factors.

It is important to recognize that risk estimation is based on group averages, which are largely driven by chronological age and may underestimate event rates in certain higher risk individuals, such as survivors of cancer. For survivors of cancer at intermediate risk of ASCVD, the use of risk modifiers such as a family history, estimated lifetime ASCVD risk, low density lipoprotein cholesterol serum levels, high-sensitivity C-reactive protein, coronary artery calcium score, or ankle brachial index may be useful for more accurately refined ASCVD risk estimation (ACC/AHA Class IIb, Level of Evidence C). The most important part of risk estimation, particularly for those for whom a treatment decision is not obvious, is communication of risk and an effective provider-patient discussion on the potential benefit of lifestyle and treatment interventions.

Life's Simple 7

The AHA developed a framework called Life's Simple 7 (Table 1), which includes both ideal health behaviors (nonsmoking, normal body mass index, physical activity at goal levels, and a healthy diet) and ideal health factors (cholesterol <200 mg/dL, blood pressure <120/<80 mm Hg, and a fasting glucose <100 mg/dL).16 Adherence to these factors promotes overall cardiovascular health and lowers the incidence of CVD (Figure 1).17 Results from the ARIC (Atherosclerotic Risk in Communities) study, with a median follow-up of 18.7 years, showed separation of the incident CVD curves within the first 5 years (Figure 2). It is then reasonable to infer that survivors of cancer with a life expectancy of at least 5-10 years would be expected to benefit from adopting Life's Simple 7.

Figure 1

Figure 2

There is concern that many of these metrics are absent or underemphasized in survivors of cancer. Patients with cancer in the Community Southern Cohort had a median of 3 healthy behaviors with only 0.9% achieving 6-7, compared with 1.7% in controls without cancer (p < 0.001).18 An analysis of survey data in 2007 revealed that more the majority of survivors of cancer did not report discussions on diet (30%), smoking (42%), or exercise (26%).19 As emphasized in numerous guidelines (Table 1), CVD prevention begins with effective discussions on lifestyle changes. With an ever-greater emphasis on value and efficiency in health care delivery, the quality time for such interactions between provider and patient becomes an increasingly valuable resource. The success of these interactions is critical for integration of primary prevention of CVD into cancer survivorship.

Collateral Benefits

The benefit of adherence to Life's Simple 7 extends beyond CVD prevention and may decrease the incidence of cancer. An analysis from the ARIC study showed a 51% relative risk reduction of incident cancer for those with 6-7 healthy metrics.20 Such findings reinforce the concept that cancer and CVD are not necessarily competing risks but are both driven by shared risk factors. Modifying these shared risk factors may jointly attenuate the top two causes of death in Western society.

Conclusions

The transition to long-term survivorship of cancer is a cause for celebration but poses risk for a myopic focus that fails to account for long-term health risks beyond cancer such as CVD. Integrating CVD prevention efforts is important to preserve the health won back from cancer. Modification of traditional risk factors via the application of primary prevention guidelines will likely attenuate risk more than specific efforts directed toward individual cancers. Such recommendations are easier to digest and assimilate for primary care providers who are often unfamiliar with the details of cancer therapies.

There is evidence that adherence to healthy behaviors and factors may reduce the risk of both CVD and cancer. This concept underscores the benefit of partnership between cardiology and oncology. Coordination between the two groups in both guideline writing and structuring of the survivorship stage will go a long way in improving the prevention of CVD in survivors of cancer.

Institute of Medicine and National Research Council (Hewitt M, Greenfield S, Stovall E, eds). From Cancer Patient to Cancer Survivor: Lost in Transition. Washington, DC: The National Academies Press; 2006.

James PA, Oparil S, Carter BL, et al. 2014 evidence-based guideline for the management of high blood pressure in adults: report from the panel members appointed to the Eighth Joint National Committee (JNC 8). JAMA 2014;311:507-20.